Multidetector Computed Tomography
In stable patients with suggested ACS with a low or intermediate probability of CAD ( coronary artery disease), in whom follow-up ECG and cardiac biomarker measurements are normal, performance of a noninvasive coronary imaging test (i.e., coronary CT angiography [CCTA]) is reasonable as an alternative to stress testing or selective coronary angiography .

CCTA has a very high negative predictive value for the detection of coronary atherosclerosis with or without significant stenosis and may be a potential alternative to stress imaging in the emergency department setting in patients at low to intermediate risk for CAD .

Large prospective trials attest to the high negative predictive value and good prognosis of a “normal” CTA in patients with low-risk acute chest pain. The advantages of cost and time savings while maintaining safety in the emergency department have also been pursued [.

In addition, CT has a well-established role in identifying aortic aneurysms, aortic dissections, pulmonary embolism, pericardial disease, and lung parenchymal disease, all of which can also present with acute chest pain ].

Evaluation of patients with CCTA results may be limited in patients with high heart rates (>65 beats/min) uncontrolled by beta blocker or other rate-limiting agents, and in patients who have intractable arrhythmias.
Patients who have calcium scores greater than 400–600 Agatson Units have limitations, although the role of calcium score in the acute setting has not been established .

Chest Pain Suggestive of ACS
Recent advances in cardiac CT imaging technology allow for further radiation dose reduction in CCTA examinations ; new and available dose-reducing techniques include prospective triggering , adaptive statistical iterative reconstruction , and high-pitch spiral acquisition .

However, these newer low-dose techniques may not be appropriate in all patients due to their dependency on a combination of factors, including heart rate, rhythm, and large body size.
Thus, although these techniques are promising in terms of reducing patient radiation dose, there may be patients for whom these radiation dose techniques are not optimal, such as an obese, elderly patient with an arrhythmia who might best benefit from retrospective gating in order to allow assessment of the coronary arteries at multiple phases of the cardiac cycle. In addition, not all scanners are capable of all radiation dose reduction techniques.

In all cases, the imaging physician must select the appropriate combination of imaging parameters to acquire a diagnostic examination at a radiation dose that is as low as reasonably achievable